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compounds. Different structures schematically drawn (types. I-III) such as the half-sandwich type I or the sandwich type II were found, in which the m...
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Inorg. Chem. 1997, 36, 1813-1820

1813

Synthesis and Crystal Structure Determination of Bifunctional Phosphine-Linked Triplatinum Double-Cluster Complexes Daniel Imhof,† Urs Burckhardt,† Klaus-Hermann Dahmen,*,†,‡ Felix Joho,† and Reinhard Nesper† Laboratorium fu¨r Anorganische Chemie, ETH, Zu¨rich, Switzerland, and Department of Chemistry and MARTECH, The Florida State University, Tallahassee, Florida 32306-3006 ReceiVed July 18, 1996X

Reactions of [Pt3(µ-CO)3(PCy3)3] (1) and [Pt3(µ-CNXyl)2(µ-CO)(CNXyl)(PCy3)2] (2) (Cy ) C6H11, Xyl ) C8H9) with 1/2 equiv of a bifunctional metal phosphine cation [(MPR′2)2(R)]2+ (M ) Cu, Ag, Au; R ) C6H4, (CH2)2C6H4, Fe(C5H5); R′ ) C6H5, C6H11) yielded quantitatively [{Pt3(µ-CO)3(PCy3)3}2{(MPR′2)2 (R)}]2+ and [{Pt3(µ-CNXyl)2(µ-CO)(CNXyl)(PCy3)2}2{(MPR′2)2(R)}]2+, respectively. The compounds were characterized by IR-, MS-, and 31P-NMR spectroscopy. The X-ray structure is given for [{Pt (µ-CO) (PCy ) } {(AuPPh ) (CH ) C H )}][PF ] 3 3 3 3 2 2 2 2 2 6 4 6 2 (14), which crystallizes in the triclinic space group P1h with Z ) 1, a ) 15.350 Å, b ) 17.150 Å, c ) 20.446 Å, R ) 84.54°, β ) 84.84°, and γ ) 64.56°. The structure was refined to R ) 0.0435 for the 8430 observed reflections (I > 3σ(I)).

Introduction Trinuclear platinum clusters such as [Pt3(µ-CO)3(PR3)3], [Pt3(µ-CNR)2(µ-CO)(CNR)(PR3)2], [Pt3(µ-CNR)3(CNR)2(PR3)], and [Pt3(µ-SO2)3-x(µ-L)x(PR3)3] (L ) CNXyl, Cl, SO2, CO) can form heterometallic clusters by reaction with many metalcontaining units, ML (Table 1).1-16 In order to understand qualitatively the bonding ability of the triplatinum clusters, the most important frontier orbitals must be considered, Scheme 1. The formation of heterometallic clusters can be explained by HOMO-LUMO interaction of the Pt3 cluster and the heterometallic unit or vice versa. Thus the * Author to whom correspondence should be addressed at Florida State University. † ETH-Zu ¨ rich. ‡ Florida State University (new address). X Abstract published in AdVance ACS Abstracts, March 15, 1997. (1) Albinati, A.; Dahmen, K.-H.; Togni, A.; Venanzi, L. M. Angew. Chem. 1985, 97, 760. (2) Imhof, D.; Burckhardt, U.; Dahmen, K.-H.; Ru¨egger, H.; Gerfin, T.; Gramlich, V. Inorg. Chem. 1993, 32, 5206. (3) Bhaduri, S.; Sharma, K.; Jones, P. G.; Erdbrugger, C. F. J. Organomet. Chem. 1987, 329, C46. (4) Bour, J. J.; Kanters, R. P. F.; Schlebos, P. P. J.; Bosman, W. P.; Behm, H.; Beurskens, P. T.; Steggerda, J. J. J. Organomet. Chem. 1987, 329, 405. (5) Braunstein, P.; Freyburger, S.; Bars, O. J. Organomet. Chem. 1988, 352, C29. (6) Briant, C. E.; Wardle, R. W. M.; Mingos, D. M. P. J. Organomet. Chem. 1984, 267, C49. (7) Dahmen, K.-H. Thesis, ETH 8172, 1986. (8) Hallam, M. F.; Mingos, D. M. P.; Adatia, T.; McPartin, M. J. Chem. Soc., Dalton Trans. 1988, 355. (9) Hill, C. M.; Mingos, D. M. P.; Powell, H.; Watson, M. J. J. Organomet. Chem. 1992, 441, 499. (10) Mingos, D. M. P.; Wardle, R. W. M. J. Chem. Soc., Dalton Trans. 1986, 73. (11) Mingos, D. M. P.; Oster, P.; Sherman, D. J. J. Organomet. Chem. 1987, 320, 257. (12) Payne, N. C.; Ramachandran, R.; Schoettel, G.; Vittal, J. J.; Puddephatt, R. J. Inorg. Chem. 1991, 30, 4048. (13) Stockhammer, A.; Dahmen, K.-H.; Gerfin, T.; Gramlich, V.; Peter, W.; Venanzi, L. M. HelV. Chim. Acta 1991, 74, 989. (14) Ezomo, O. J.; Mingos, D. M. P.; Williams, I. D. J. Chem. Soc., Chem. Commun. 1987, 924. (15) Albinati, A.; Dahmen, K.-H.; Demartin, F.; Forward, J. F.; Longley, C. J.; Mingos, D. M. P.; Venanzi, L. M. Inorg. Chem. 1992, 31, 2223. (16) Albinati, A.; Moor, A.; Pregosin, P. S.; Venanzi, L. M. J. Am. Chem. Soc. 1982, 104, 7672.

S0020-1669(96)00846-4 CCC: $14.00

resulting products can be considered “Lewis acid-base addition” compounds. Different structures schematically drawn (types I-III) such as the half-sandwich type I or the sandwich type II

were found, in which the metal center is linked to one or two cluster units. Furthermore, a bicapped type III is known in which the Pt3 building block is capped by a metal fragment ML on both sides. Many of these compounds can be successfully used as precursors in heterogeneous catalysis.17,18 Recently we found that [Pt3(µ-CO)3(PR3)3] and its heterometallic derivatives are active catalysts in the dehydrogenation of methylcyclohexane to toluene.19 Moreover, triangular clusters such as [Pt3(µ-CO)3(CO)3]2can stack to clusters [Pt3(µ-CO)3(CO)3]n2-, n ) 1-10, which show an extraordinary redox behavior that depends on the stacking size.20 Due to their geometric arrangement and “electron buffer abilities” clusters may be considered as useful building blocks for the systematic approach to molecular networks and macromolecules. In principle there are three possible pathways to combine two Pt3 units: (1) surface linking, (2) terminal ligand linking, and (3) bridge ligand linking (Figure 1). This approach is not new; e.g., Vahrenkamp and co-workers have used bifunctional phosphines such as PPh2RPPh2 (R ) p-C6H4 or 4,4′-C6H4-C6H4) for the preparation of double (17) Mu¨ller, S. Thesis, ETH 11160, 1995. (18) Braunstein, P.; Bender, R.; Kervennal, J. Organometallics 1982, 1 (9), 1236. (19) Ichikawa, M. J. Chem. Soc., Chem. Commun. 1976, 11. (20) Longoni, P.; Chini, P. J. Am. Chem. Soc. 1976, 98 (23), 7225.

© 1997 American Chemical Society

1814 Inorganic Chemistry, Vol. 36, No. 9, 1997

Imhof et al.

Table 1. Trinuclear Clusters Which Can Form Heterometallic Clusters by Reaction with Many Different Metal-Containing Units

a

building block {B}

Lewis-acid/-base

product

[Pt3(µ-CO)3(PR3)3] [Pt3(µ-CO)3(PR3)3] [Pt3(µ-CO)3(PR3)3] [Pt3(µ-CO)3(PR3)4] [Pt3(µ-Cl)(SO2)2(PR3)3] [Pt3(µ-CNXyl)(SO2)2(PR3)3] [Pt3(µ-CNR)x(µ-CO)3-x(CNR)y(PR3)3-y]c [Pt3(µ-CO)3(PR3)3] [Pt3(µ-CO)3(PR3)3] [Pt3(µ-CO)3(PR3)3]

MPR3+ a M+ a MXnb MPR3+ a AuPR3+ AuPR3+ MPR3+ a Hg(0) Tl(I) Hg2X2

[{B}{MPR3}]+ [{B}2M]+ [{B}{MXn}]+ [{B}{MPR3}]+ [{B}{AuPR3}2]+ [{B}{AuPR3}]+ [{B}{MPR3}]+ [{B}2Hg] [{B}Tl]+ [{B}{HgX}2]

M ) Cu(I), Ag(I), Au(I). b MXn ) ZnX2, CdX2, InX3.

c

type I II II II III II II I II III

ref 6 1, 8 13 3-5 11 9 2 16 14 15

x ) 2, y ) 1, or x ) 3, y ) 2.

Figure 1. The three possible pathways to combine two Pt3 units via (1) cluster-surface linking, (2) terminal ligand linking, and (3) bridge ligand linking.

Scheme 1

clusters.21 In their research they have used Co3(CO)9, FeCo2(CO)9, HFe2Co(CO)9, and H2Fe3(CO)9 as M3 units. In this paper we will discuss the synthesis and charaterization of bifunctional phospine-linked triplatinum clusters [Pt3(µ-CO)3(PR3)3], [Pt3(µ-CNR)2(µ-CO)(CNR)(PR3)2], and [Pt3(µ-CNR)3(CNR)2(PR3)] (Figure 2). Results Phosphines. For the preparation of double (two cluster units per molecule) and triple clusters (three cluster units per molecule) appropriate bi- and trifunctional phosphines had to be synthesized with a delocalizable electronic system and a rigid molecular structure that cannot chelate the metal center. Numerous phosphine ligands fulfill these requirements.22,23 In order to study the structural and electronic behavior, we prepared (21) Honrath, U.; Shu-Tang, L.; Vahrenkamp, H. Chem. Ber. 1985, 118, 132.

Figure 2. Cluster systems using delocalizable organometallic molecules as bridging units between the Pt3 clusters.

bifunctional phosphines with cyclohexyl and phenyl groups (Figure 3). While the phosphines 38 and 42 were synthesized according to the literature via a Birch reaction,22 39-41 and 43 were prepared via the corresponding PR2Cl or PR2H with R ) Ph and Cy.24,25 These compounds were characterized by elemental analysis and IR- and 31P-NMR spectroscopy. Chemical shifts of the 31PNMR spectra for all isolated bi- and trifunctional phosphines are given in the Experimental Section. Gold, Copper, and Silver Phosphine Cations. The copper and silver phosphine cations were synthesized directly from the reaction of Cu(CH3CN)4PF6 and AgBF4 with the bifunctional phosphines. The gold phosphine cations were synthesized in situ by addition of TlPF6 to the gold phosphine chlorides [1,4(AuClPPh2)2C6H4] (44), [1,4-(AuClPCy2)2C6H4] (45), [1,4(AuClPPh2CH2)2C6H4] (46), [1,4-(AuClPCy2CH2)2C6H4] (47), [1,3,5-(AuClPPh2)3C6H3] (48), and [1,1′-(AuClPPh2)2Fe(ηC5H5)2] (49). All gold phosphine chlorides were synthesized according to the literature26 by reducing NaAuCl4‚2H2O with thiodiglycol. While older methods27,28 used an excess of phosphine, as both a reagent and as reducing agent, this is unnecessary in the current method which leads to high yields of pure gold phosphine chlorides. They were identified by elemental analysis and IR and 31P-NMR spectroscopy. The 31PNMR chemical shifts of these compounds are given in the Experimental Section. Double/Triple Clusters. Just as the Lewis acids CuPR3+, AgPR3+, and AuPR3+ (in situ) react with [Pt3(µ-CO)3(PCy3)3] (1) and [Pt3(µ-CNXyl)2(µ-CO)(CNXyl)(PCy3)2] (2) to give the addition products of type I,2,6 the bifunctional copper, silver, and gold phosphine cations form the analogous double and triple (22) (23) (24) (25) (26)

McFarlane, H. C. E.; McFarlane, W. Polyhedron 1988, 7, 1875. Cotton, F. A.; Hong, B. Prog. Inorg. Chem. 1992, 40, 179. Baldwin, R. A.; Chen, M. T. J. Org. Chem. 1966, 32, 1572. Herring, D. L. J. Org. Chem. 1961, 26, 3998. Sutton, B. M.; McGusty, E.; Walz, D. T.; Dimartino, M. J. Med. Chem. 1972, 15, 1095. (27) McAuliffe, C. A.; Parish, R. V.; Randall, P. D. J. Chem. Soc., Dalton Trans. 1979, 1730. (28) Carioti, F.; Naldini, L.; Simonetta, G.; Malatesta, L Inorg. Chim. Acta 1967, 1, 315.

Triplatinum Double-Cluster Complexes

Inorganic Chemistry, Vol. 36, No. 9, 1997 1815

Figure 3. Bi- and trifunctional phosphines with cyclohexyl and phenyl groups.

Figure 5. ORTEP view of 14, showing the core atoms.

Discussion Figure 4. Synthesis of double and triple clusters. Table 2. All the Compounds That Have Been Synthesized in This Study

clusters. For [Pt3(µ-CNXyl)3(CNXyl)2(PCy3)] (22) only the reaction with the gold phosphine cations led to the isolation of 23 and 24. The products of the reaction with the copper and silver phosphine cations decomposed quickly and as a result could not be identified.29 The syntheses of all isolated double and triple clusters were identical. A solution of the clusters (1, 2, or 22) in THF or CH2Cl2 was reacted with 1/2 equiv of metal phosphine cation. The reaction was complete within minutes, indicated by a color change to deep red. By addition of hexane the cationic bi/trifunctional clusters were isolated quantitatively (Figure 4). With all of the described bifunctional phosphines, heterometallic double clusters of the half-sandwich type I were synthesized. While the resulting copper and gold clusters could be isolated in high yields, the reactions with the silver compounds were often incomplete and resulted in decomposition products. Table 2 shows all the compounds that have been synthesized in this project. (29) Imhof, D. Thesis, ETH 10850, 1994.

The stability of the heterometallic platinum clusters can be correlated with the Lewis acidity strength of the metal cations. Thus the most acidic Au+ (pKhyd. < 4) coordinates stronger than the less acidic Cu+ and Ag+ (pKhyd. ca. 6.9).30 The following order has been determined empirically from the tendency of formation and stability of the obtained compounds: Au+ > Cu+ > Ag+. In this context the behavior of the sandwich clusters of type II toward metal hydrides emphasizes this trend. While the gold compounds do not undergo any reaction, both copper and silver sandwich clusters react completely to form new hydride clusters.31 The behavior of the double and triple clusters is almost identical to that of the half-sandwich type I. In this case we observed that the gold and copper half-sandwich clusters are more stable than the analogous silver compounds. The latter decompose slowly in solution to the thermodynamically more stable sandwich compounds of type II. X-ray Structure Determination. Small bright rhombohedron-shaped crystals of the double cluster cation [{Pt3(µ-CO)3(PCy3)3}2{(AuPPh2)2(CH2)2C6H4}]2+ (14) have been obtained by slow diffusion of cyclohexane into a solution of 14 in chloroform. An ORTEP view of 14 of the core atoms is shown in Figure 5. Selected bond lengths and bond angles are given in Table 3, and a full list can be found in the Supporting Information. The X-ray crystal structure of 14 reveals that this compound consists of discrete Pt-Au cations and PF6- anions. The gold atom caps the triangular Pt3 unit forming a slightly distorted Pt3Au tetrahedron with Au-Pt distances between 2.7666(13) and 2.7283(10) Å at 150 K. These values Pt-Au distances of 2.750-2.768 Å are within the same range as those for [{Pt3(µ-CO)3(PCy3)3}{AuPCy3}]+ (33).6 Similary, the Pt-Pt bond lengths are comparable for both compounds 14 and 33, with average Pt-Pt bond length of 2.666(1) and 2.682(9) Å, respectively. However, due to the coordination of the gold phosphine cation to [Pt3(µ-CO)3(PCy3)3], an average lengthening of the Pt-Pt bond of 0.02 Å for the (30) Yatsimirskii, K. B.; Wassiljew, V. P. Instability Constants of Complex Compounds; Pergamon Press: Elmsford, N.Y, 1960. (31) Imhof, D.; Fadini, L.; Dahmen, K.-H.; Venanzi, L. M. Publication in preparation.

1816 Inorganic Chemistry, Vol. 36, No. 9, 1997

Imhof et al.

Table 3. Selected Bond Lengths (Å) and Bond Angles (deg) of 14 and 33 14

33

Pt(1)-Pt(2) Pt(1)-Pt(3) Pt(2)-Pt(3) Pt(1)-Au Pt(2)-Au Pt(3)-Au

2.6644(8) 2.6701(13) 2.6627(8) 2.7666(13) 2.7283(10) 2.7333(12)

Bond Lengths 2.663(1) Pt-P(av) 2.670(3) Pt(1)-C(2) 2.663(1) Pt(2)-C(3) 2.765(1) Pt(3)-C(1) 2.728(1) C-O(av) 2.733(1)

Pt(1)-Pt(2)-Pt(3) Pt(1)-Pt(3)-Pt(2)

60.16(3) 59.95(3)

60.2(0) 59.9(0)

14

33

2.274(3) 2.08(2) 2.04(2) 2.074(14) 1.18 (2)

2.273(1) 2.047(1) 2.046(1) 2.057(1) 1.182(1)

59.89(3) 58.01(2)

59.9(0) 58.0(0)

Angles Pt(3)-Pt(1)-Pt(2) Pt(1)-Au-Pt(2)

double cluster 14 and 0.035 Å for the half-sandwich cluster 33,6 with respect to the uncoordinated cluster, can be observed. These differences might be directly related to the different Lewis basicities of the phosphine (in 14 the arylphosphine is less basic than the alkylphosphines in 33) that is coordinated at the gold atom. A look at the changes in the torsion angles of the ligands to the Pt3 plane is interesting. In the uncoordinated cluster 1, both the phosphine and carbonyl ligands are bent by an average angle of 15° out of the Pt3 plane (Figure 6) in opposite directions to each other.32 The coordination of the gold phosphine cation changes the positions of the ligands. While the phosphines are bent with an average angle of 20° away from the Pt3 plane from the gold phosphine cation, the carbonyl ligands are almost in plane (Figure 7). These torsion angles are not equal for all ligands. For the double cluster 14, one of the three CO ligands is bent away by 3° more than the others and one of the PR3 ligands is bent by 9-10° closer toward the Pt3 plane than the other two (Table 4). This behavior is exactly contrary to that seen in the mercury(0) clusters where the phosphines are bent toward the metal and the carbonyl ligands are bent away from the metal (Figure 6).16 This confirms the different type of interaction that has been reported in the mercury(0) adduct clusters.33

The FAB(+) MS is a very useful tool for the verification of the predicted structure of this large cluster. The parent peak is that of the cluster cation ([MPF6]+). The contribution of isotopes can be simulated and used as a fingerprint for the identification of the cluster structure. This helped us to identify the ferrocenyl-platinum cluster [{[1,1′-(AuPPh2)2Fe(η-C5H5)2}{Pt3(µ2-CO)3(PCy3)3}2][PF6]2 (27), sketched schematically in Figure 8. Although this compound crystallizes easily, all attempts failed in obtaining suitable crystals for X-ray diffraction. IR Spectroscopy. The changes in the electronic structure of the [Pt3(µ-CO)3(PR3)3] unit caused by addition of Lewis acids are shown in the ν(CO) frequencies in the IR spectra and in the 31P-NMR data. In the IR spectra, the CO frequencies of the double cluster are at 1798-1800 cm-1 (st) and 1768-1787 cm-1 (m). Compared to the free cluster 1 (ν(CO) ) 1764, 1738 cm-1), a shift of 30 cm-1 to higher frequencies can be observed. Compared to the free cluster [Pt3(µ-CNXyl)2(µ-CO)(CNXyl)(PCy3)2] (2), the same behavior can also be observed for the terminal isonitrile ligand and the bridging carbonyl ligand of the addition products 8 and 20 with a shift toward higher frequencies of 20 and 40 cm-1, respectively. The trend of shifting to higher frequencies by the coordination of a metal fragment to the building block Pt3 would suggest a weakening of the π-back-bonding from the platinum to the carbonyl ligand which would cause a lengthening of the M-CO bond and a strengthening of the C-O bond. However, such bond length changes cannot be confirmed by the X-ray structure. In 14 the C-O bond lengths are almost equal to those in 1, and those in 33 are even longer (1.28(2) Vs 1.19(4)).6 A possible explanation might be the change of the torsion angles discussed above and the possible dynamics of carbonyl ligands in the cluster. A correlation between the IR shift frequencies and the C-O bond length cannot be easily given. NMR Spectroscopy. All of these compounds give a characteristic pattern in 31P{1H}-NMR spectroscopy caused by the arrangement of the active isotopes 195Pt (natural abundance, na ) 33.7%) and 31P (na ) 100%) in the cluster skeleton. The exact explanation of the NMR patterns of [Pt3(µ-CO)3(PR3)3], [Pt3(µ-CNR)2(µ-CO)(CNR)(PR3)2], and [Pt3(µ-CNR)3(CNR)2(PR3)] is given in the references. However, in order to understand the 31P-NMR spectrum shown in Figure 9, we give a brief explanation here. The spectrum of the [Pt3(µ-CO)3(PCy3)3]-unit 1 is mainly a linear combination of the signals of two of the isotopomers with the highest natural abundance A3 and A2A′X.7 By substitution of one phosphine and two carbonyl ligands in 1 with isonitrile ligands, the cluster [Pt3(µ-CNXyl)2(µ-CO)(CNXyl)(PCy3)2] (2) is formed. The symmetry of the system decreases from D3h to C2V. Therefore the number of possible isotopomers increases from 4 to 6.2,34 The spin systems of the most important

(32) Albinati, A. Inorg. Chim. Acta 1977, 22, L31.

(33) Gade, L. H. Angew. Chem., Int. Ed. Engl. 1993, 32, 24.

Figure 6. Torsion angles of the ligands to the Pt3 plane of the tetrahedral gold cluster 11 and the mercury cluster.

Figure 7. Projection of the Pt3 plane in 11.

Triplatinum Double-Cluster Complexes

Inorganic Chemistry, Vol. 36, No. 9, 1997 1817

Table 4. Torsion Angles (deg) of the Phosphine and Carbonyl Ligands of 1, 14, and 3332 torsion angles (χ)

1

33

14

torsion angles (φ)

1

33

14

Pt(1)-Pt(2)-Pt(3)-C(1) Pt(1)-Pt(2)-Pt(3)-C(2) Pt(1)-Pt(3)-Pt(2)-C(3)

16.5 7.6 18.2

5.8 1.6 0.8

2.6 1.8 5.4

Pt(2)-Pt(3)-Pt(1)-P(1) Pt(1)-Pt(3)-Pt(2)-P(2) Pt(1)-Pt(2)-Pt(3)-P(3)

-15.5 -13.3 -18.2

-20.9 -20.4 -17.4

-25.3 -27.7 -15.1

Figure 8. Schematic Drawing of [{[1,1′-(AuPPh2)2Fe(η-C5H5)2}{Pt3(µ2-CO)3(PCy3)3}2][PF6]2 (27).

isotopomers are A2, AA′X, and A2X. Further substitution of one CO and one PR3 in 2 forms the cluster [Pt3(µ-CNXyl)3(CNXyl)2(PCy3)] (22). Due to the single phosphorus atom in 22, the subspectra of the isotopomers are exclusively of first order and the spectrum can be easily interpreted.2,34 By the coordination of the metal phosphine cation, an additional phosphorus is introduced which leads to a further splitting of the signals in the spectra. This gives additional information about the structure in solution and about the bonding of the metal fragment to the cluster. For all the gold compounds a quartet with platinum satellites is found. This points out that the gold phosphine unit is bonded symmetrically to the Pt3 triangle forming a Pt3Au tetrahedron. Due to the structural symmetry of the gold double clusters, with a C3 axis mirror plane or an inversion center, both Pt3Au tetrahedrons are chemically equivalent and do not differ in the NMR spectrum. Therefore the spectra are almost identical to those of the halfsandwich compounds.6 This is also the case for the copper and silver compounds. The situation in the 31P-NMR spectra of the copper analogues is identical. However due to the fact that the natural isotopes 63Cu and 65Cu have spin I ) 3/ and a high electromagnetic 2 moment, the signals are broadened, especially the signal of the phosphorus that is directly bonded to the copper atom. The determination of all coupling constants is therefore not easy to achieve. The fact that silver has two NMR active isotopes, 107Ag (51.84%) and 109Ag (48.16%) with spin I ) +1/2 leads in the 31P{1H}-NMR spectrum of the silver addition products to a further splitting of the NMR pattern discussed above (Figure 9). For example, in the simple case without NMR-active platinum, the phosphine on the silver (PM) gives rise to two doublets of quartets caused by the coupling to one of the silver isotopes and the three phosphorous atoms of the Pt3 unit. Because 109Ag has the higher gyromagnetic moment compared to 107Ag, all signals of this mutliplet are split twice. In a comparison of the double cluster and the half-sandwich clusters, only slight but significant changes in the chemical shift and coupling constants of the NMR spectra can be seen (Table (34) Briant, C. E.; Gilmour, D. I.; Mingos, D. M. P.; Wardle, R. W. M. J. Chem. Soc., Dalton Trans. 1985, 1693.

Figure 9. 31P{1H}-NMR spectrum of 16: (Top) experimental spectrum; (bottom) simulated spectrum.

5). One reason for this behavior is certainly the fact that the basic unit is always the same and the changes can only be affected by the coordinated groups. The other reason is the organic groups are in general too large for sufficient spin-spin interaction of one cluster unit to the other. Because the building block [Pt3(µ-CO)3(PCy3)3] (1) remains the same for all of the synthesized half-sandwich- and doublecluster compounds described here, the influence of the electronegativity of the metal fragment MPR3+ on the 31P-chemical shifts δ and coupling constates can be studied. The phosphorus of the Pt3 unit (P) and the phosphorus of the added metal fragment MPR3 (PM) have different chemical shifts. The chemical shifts δ(P) of the cluster phosphines move approximately 10-12 ppm upfield upon coordination of a metal fragment MPR3+ and are not strongly influenced by the different metals in the MPR3+ unit. In the case of the 31P-NMR chemical shifts δ(P*) the effects of the R groups are even more pronounced and show a strong relationship with the following metal ions: Cu+, Ag+, Au+. The change in the electronic structure of the Pt3-cluster unit caused by “addition” of the other metal fragments is clearly shown by comparing the 1J(Pt,P) coupling constants. The 1J(Pt,P) values are significantly larger for the heterometallic clusters than for the uncoordinated clusters (4670-4870 Hz Vs 4410 Hz). An increase of the 1J(Pt,P) for MPR3+ (R ) Ph, Cy) follows the order Cu+ > Ag+ > Au+. In general the 1J(Pt,P) values of the same compounds are larger for the phenylcontaining MPR3+ (M ) Cu+, Ag+) than for those containing cyclohexyl groups. A more precise analysis of the NMR data is given in the Supporting Information.

1818 Inorganic Chemistry, Vol. 36, No. 9, 1997 Table 5.

cmpd 1

1 22 31 41 51 62 72 82 91 101 111 121 131 141 151 161 171 182 192 202 211 223 233 243 251 261 271 281 291 301 311 321 331 342 352 362 373

Imhof et al.

31

P{1H}-NMR Data for all Double and Triple Clusters

δP 69.8 71.3 58.3 59.4 58.1 56.0 58.8 54.8 56.0 57.0 56.2 56.1 57.0 55.9 56.0 56.9 54.6 55.9 57.9 53.6 56.1 58.3 40.6 44.3 56.1 56.9 52.2 55.9 56.9 59.1 56.0 56.9 51.9 56.8 59.7 55.9 45.9

δPM

1

53.2 65.6 55.5 51.1 54.5 52.7 51.2 64.8 83.9 51.1 63.1 59.2 51.0 63.0 77.5 41.0 62.9 62.9 54.0 67.6 61.6 51.5 63.0 52.8 50.7 62.8 55.7 51.0 63.0 82.7 41.5 55.3 78.4 73.2

J(Pt,P) 4412 4102 4673 4797 4877 4456 4501 4699 4659 4766 4904 4669 4782 4911 4664 4778 4921 4414 4521 4685 4875 3877 4411 4442 4668 4799 4927 4727 4791 4868 4657 4776 4899 4453 4506 4665 4401

2

J(Pt,P)

430 435/439 303 286 257 332/302 304/271 284/258 303 285 272 303 288 268 303 285 280 333/303 316/283 294/270 256 446 321/321 313/313 303 287 269 315 305 260 307 286 282 335/312 315/284 301/271 323/237

2

J(Pt,PM)

122 139 230 131/131 120/120 217/217 123 138 189 127 144 213 106 152 182 138/138 129/129 197/197 240 238/274 223/298 119 140 176 127 149 235 121 138 177 125/125 135/135 179/179 270/270

Summary and Conclusions Platinum carbonyl phosphine cluster of the type [Pt3(µ-CO)3(PR3)3] react with polyfunctional d10 metal phosphine cations [(MPR′2)n(R′′)]n+ (n ) 2, 3; R′′ ) C6H4, (CH2)2C6H4; M ) Cu, Ag, Au) to form double and triple clusters [{Pt3(µ-CO)3(PR3)3}n{(MPR′2)n(R′′)}]n+ (n ) 2, 3). The crystal structure of [{Pt3(µ-CO)3(PCy3)3}2{(AuPPh2)2(CH2)2C6H4)}][PF6]2 shows one representative of this new class of compounds. Their reactivity and stablity is very similar to that of the corresponding half-sandwich clusters [{Pt3(µ-CO)3(PCy3)3}{(MPR′3}]+. Although the platinum isonitrile carbonyl phosphine clusters of the type [Pt3(µ-CNXyl)2(µ-CO)(CNXyl)(PR3)2] allow the synthesis of the copper, silver, and gold double clusters, only the gold double cluster was obtained for the platinum isonitrile phosphine clusters of the type [Pt3(µ2-CNXyl)3(CNXyl)2(PR3)}2]. Due to the high symmetry of all these clusters the spectroscopic data are very similar. No large differences between the chemical shifts or coupling constants of the phenyl- and benzylcontaining bridging ligand were found that would lead to the conclusion of a possible delocalized electron conjugated system. The differences found are mainly caused by the differences in the Lewis acidity of the metal center as well as by the Lewis basicities of the phosphines on the platium cluster. These effects

3

J(P,P′) 58 56 31 28 25 33 23.5 23.5 30 26.6 26 30.7 28.2 27.5 32 29 27 33 28 28 25.2

31 27.8 25.3 30 29 25 28.7 28 25 34.5 28 29.5

3

1

J(P,PM)

11.3 10.5 25 11.1 7.7 22.4 10.2 10.8 26 11.2 10.5 27.5 11.3 10.1 27 10.3 9.5 23.2 25.2 15.1 16.7 10.7 10.7 25.3 12 10.5 25 10.0 9.3 25 8.5 7.5 20.5 20

J(Pt,Pt′)

-1548 -1050/-325 -2080 -2010 -2050 -1990 n.o. -1950 -1887 n.o. -2080 -1944 n.o. -2015 -1975 -1990 -2100 n.o. n.o. -1925 -2030 n.o. n.o. -2075 -2030 -2145 n.b. -2068 -2020 -1986 -1875 -2100 n.b. n.b.

1

J(Ag,PM)

2

J(Ag,P)

605/524

28/28

651/564

27/27

551/477

28/28

588/510

28/28

608/525

28/28

661/574

28/28

606/526

28/28

624/

27/27

572/

26/26

627/553

28/28

are similar to those observed for the corresponding halfsandwich compounds. Experimental Section Reactions were routinely carried out using standard Schlenk line procedures under an atmosphere of pure argon and using dry O2-free solvents. The compounds [1,4-(PPh2)2C6H4] (38),22 [1,3,5-(PPh2)3C6H3] (42),22 [1,1′-(PPh2)2Fe(η-C5H5)2] (43),35 [Au(PPh3)Cl],22 [Au(PCy3)Cl]22, [1,4-(AuClPPh2)2C6H4] (44),22 [1,1′-(AuClPPh2)2Fe(η-C5H5)2] (49),36 [Pt3(µ-CO)3(PCy3)3] (1),37 [Pt3(µ-CNXyl)2(µ-CO)(CNXyl)(PCy3)2] (2),34 and [Pt3(µ-CNXyl)3(CNXyl)2(PCy3)] (22)34 were prepared as described in the literature. Infrared spectra were recorded on a Perkin-Elmer 883 spectrometer as RbI pellets. 31P{1H}-NMR spectra were run on a Bruker AC250 spectrometer. The 31P operating frequency was 101.3 MHz. 31P{1H}-NMR were measured and reported using H3PO4 (85%) as an internal standard and Na2PtCl6, respectively. 31P{1H}-NMR simulations were carried out using a program developed by A. K. Rappe. Preparation of 1,4-Bis(dicyclohexylphosphino)benzene (39). pDibromobenzene (1.82 g, 7.73 mmol) was dissolved in Et2O (20 mL). (35) Bishop, J. J.; Davison, A.; Katcher, M. L.; Lichtenberger, D. W.; Merrill, R. E.; Smart, J. C. J. Organomet. Chem. 1971, 27, 241. (36) Hill, D. T.; Girard, G. R.; McCabe, F. L.; Johnson, R. K.; Stupik, P. D.; Zhang, J. H.; Reiff, W. M.; Eggleston, D. S. Inorg. Chem. 1989, 28, 3529. (37) Moor, A.; Pregosin, P. S.; Venanzi, L. M. Inorg. Chim. Acta 1981, 48, 153.

Triplatinum Double-Cluster Complexes A solution in hexane of n-BuLi (19.3 mL, 30.94 mmol) (1.6 M) was slowly added at 0 °C. The resulting solution was vigorously stirred for 2.5 h at 60 °C. After the solution was cooled to 0 °C, dicyclohexylchlorophosphine (3.74 mL, 17.01 mmol) was added dropwise, and the resulting solution was heated for 5 h and hydrolyzed with MeOH/H2O. The resulting solid was isolated and washed with H2O, MeOH, and Et2O to give white crystals of 39 in 22% yield. Anal. Calcd for C30H48P2: C, 76.56; H, 10.28. Found: C, 74.91; H, 10.38. IR: 2919 vs, 2849 vs, 1443 s, 1371 w, 1343 w, 1262 w, 1177 m, 1110 m, 995 m, 884 m, 851 m, 813 m, 538 m, 512 m. 1H-NMR: 7.6-7.2 (m, 4 H); 2.1-1.5 (m, 24 H); 1.5-0.8 (m, 20 H). 31P{1H}-NMR: δ(P) ) 2.0 (s). Preparation of Bis(diphenylphosphino)-p-xylene (40). Diphenylchlorophosphine (4.86 mL, 26.29 mmol) was dissolved in thf (25 mL). After the solution was cooled to 0 °C, small pieces of lithium (400 mg, 57.60 mmol) were added. After 2 h the excess of lithium was filtered off and the red solution was added dropwise to a solution of R,R′-dibromo-p-xylene (3.2 g, 12.12 mmol) in thf (20 mL). After being heated for 4 h, the mixture was hydrolyzed, filtered, and washed with H2O, MeOH, and Et2O to give white crystals in 37% yield. Concentration and cooling of the filtrate resulted in a total yield of 52%. Anal. Calcd for C32H28P2: C, 81.00; H 5.95. Found: C, 80.25; H 6.01. IR: 3062 w, 3022 w, 1582 w, 1505 m, 1475 m, 1427 m, 1082 w, 1063 w, 847 m, 825 m, 737 s, 694 vs, 526 s, 505 m, 460 w, 416 w. 1H-NMR: 7.75-7.25 (m, 24 H); 3.34 (s, 2 CH2P). 31P{1H}-NMR: δ(P) ) -11.1 (s). Preparation of Bis(dicyclohexylphosphino)-p-xylene (41). Dicyclohexylchlorophosphine (3.1 g, 15.63 mmol) was dissolved in Et2O (30 mL). A solution of n-BuLi (10.3 mL 16.50 mmol) in hexane (1.6 M) was slowly added at 0 °C with vigorous stirring. The solution was allowed to continue to stir for 30 min at room temperature. After dropwise addition of R,R′-dibromo-p-xylene (2.0 g, 7.8 mmol) in thf (25 mL), the solvent was removed by distillation and the resultant solid hydrolyzed with H2O (50 mL) and extracted with CH2Cl2 (30 mL). Crystallization from CH2Cl2/MeOH gave white crystals in 17% yield. Anal. Calcd for C32H52P2: C, 77.07; H 10.51. Found: C, 75.70; H, 10.51. IR: 2924 vs, 2847 vs, 1508 s, 1443 s, 1264 m, 1220 m, 1173 m, 1104 m, 1020 m, 998 m, 887 m, 842 s, 810 s, 539 sh, 515 m. 31P{1H}-NMR: δ(P) ) 2.0 (s). General Preparation of [Phosphine]bis[chlorogold]. NaAuCl4‚2H2O (1.22 mmol) was dissolved in MeOH (20 mL) at 0 °C, and thiodiglycine (5.50 mmol) in MeOH (4 mL) was added. Once the solution turned colorless (ca. 20 min), bis(phosphine) (0.61 mmol) in CH2Cl2 (or CHCl3) (20 mL) was added. After warming to room temperature and stirring for 2 h, the CH2Cl2 was removed. The resultant solid was filtered out and washed with MeOH to give white crystals in 85-100% yield. [1,4-Bis(dicyclohexylphosphino)benzene]bis[chlorogold] (45). Anal. Calcd for C30H48Au2Cl2P2: C, 38.52; H 5.17. Found: C, 38.57; H 5.26. IR: 2926 vs, 2849 s, 1444 m, 1379 m, 1347 w, 1297 w, 1267 w, 1201 w, 1176 w, 1119 m, 1003 m, 916 w, 888 w, 851 w, 819 m, 753 m, 559 s, 522 m, 328 m. 1H-NMR: 7.85-7.70 (m, 4 H); 2.351.00 (m, 44 H). 31P{1H}-NMR: δ(P) ) 50.8 (s). [r,r′-Bis(diphenylphosphino)-p-xylene]bis[chlorogold] (46). Anal. Calcd for C32H28Au2Cl2P2: C, 40.92; H, 3.00. Found: C, 40.26; H, 3.10. IR: 3051 m, 3019 w, 2995 w, 2913 w, 1507 m, 1479 m, 1433 s, 1411 m, 1309 w, 1222 w, 1166 w, 1100 s, 1024 w, 997 w, 839 s, 746 vs, 718 sh m, 693 vs, 535 s, 514 s, 491 m, 469 m, 435 w, 326 s. 1 H-NMR: 7.65-7.45 (m, 20 H); 6.86 (m, 4 H); 3.70 (d, 2J(1H,31P) ) 10.4 Hz, 4 H). 31P{1H}-NMR: δ(P) ) 33.3 (s). [r,r′-Bis(dicyclohexylphosphino)-p-xylene]bis[chlorogold] (47). Anal. Calcd for C32H52Au2Cl2P2: C, 39.89; H, 5.44. Found: C, 41.57; H, 5.51. IR: 2924 vs, 2848 s, 1508 m, 1443 s, 1419 w, 1297 w, 1268 w, 1204 w, 1175 w, 1111 w, 1088 w, 1003 w, 889 w, 853 m, 838 sh m, 536 m, 516 m, 321 s. 1H-NMR: 7.40 (m, 4 H); 3.20 (d, 2J(1H,31P) ) 10.3 Hz, 4 H); 2.0-1.6 (m, 24 H); 1.6-1.1 (m, 20 H). 31P{1H}NMR: δ(P) ) 47.4 (s). [1,3,5-Tris(diphenylphosphino)benzene]tris[chlorogold] (48). Anal. Calcd for C42H33Au3Cl3P3: C, 37.99; H, 2.50. Found: C, 38.81; H, 2.57. IR: 3064 m, 1667 w, 1604 m, 1586 s, 1476 m, 1455 m, 1423 s, 1310 sh m, 1291 s, 1179 m, 1124 s, 1096 s, 1025 w, 991 m, 878 m,

Inorganic Chemistry, Vol. 36, No. 9, 1997 1819 858 m, 747 s, 693 s, 672 m, 569 m, 543 m, 502 s, 461 m, 332 m. 31P{1H}-NMR: δ(P) ) 33.8 (s). General Preparation of Double Copper Compounds. Bis(phosphine) PR2R′PR2 (9.93 mmol) and [Cu(CH3CN)4]PF6 (19.86 mmol) were dissolved in CH2Cl2 (or thf) (5 mL). The mixture was added dropwise to a solution of [Pt3(µ-CO)3(PCy3)3] or [Pt3(µ-CNXyl)2(µ-CO)(CNXyl)(PCy3)2] (9.93 mmol) in CH2Cl2 (5 mL). After stirring for 30 min, the solution was concentrated to 1 mL. Addition of hexane gave a red powder in 70-91% yield. [{1,4-(CuPPh2)2C6H4)}{Pt3(µ2-CO)3(PCy3)3}2][PF6]2 (3). Anal. Calcd for C144H222Cu2F12O6P10Pt6: C, 44.52; H 5.76. Found: C, 45.75; H, 5.93. IR: ν(CO) ) 1825 sh m, 1795 vs, 1765 m. [{1,4-(CuPPh2)2C6H4)}{Pt3(µ2-CO)(µ2-CNXyl)2(CNXyl)(PCy3)2}2][PF6]2 (6). Anal. Calcd for C158H210Cu2F12N6O2P8Pt6: C, 47.46; H, 5.29; N, 2.10. Found: C, 46.50; H, 5.10; N, 1.81. IR: ν(CN,term.) ) 2135 s; ν(CN,µ), ν(CO) ) 1772 s, 1724 m, 1732 s. [{1,4-(CuPCy2CH2)2C6H4)}{Pt3(µ2-CO)(µ2-CNXyl)2(CNXyl)(PCy3)2}2][PF6]2 (18). Anal. Calcd for C160H238Cu2F12N6O2P8Pt6: C, 47.44; H, 5.92; N, 2.08. Found: C, 46.11; H, 5.75; N, 1.78 IR: ν(CN,term.) ) 2136 s; ν(CN,µ2), ν(CO) ) 1771 s, 1720 m. [{[1,1′-(CuPPh2)2Fe(η-C5H5)2}{Pt3(µ2-CO)3(PCy3)3}2][PF6]2 (25). Anal. Calcd for C148H226Cu2F12FeO6P10Pt6: C, 44.52; H 5.71. Found: C, 45.63; H, 6.11. IR: ν(CO) ) 1794 st, 1767 m. General Preparation of Double Silver Compounds. PR2R′PR2 (9.93 mmol) and AgCF3SO3 (19.86 mmol) were dissolved in CH2Cl2 (or thf) (5 mL). The mixture was dropwise added to a solution of [Pt3(µ-CO)3(PCy3)3] or [Pt3(µ-CNXyl)2(µ-CO)(CNXyl)(PCy3)2] (9.93 mmol) in CH2Cl2 (5 mL). The solution immediately turned dark red. After stirring for 30 min, the solution was concentrated to 2 mL. Addition of hexane gave a deep-red powder in 53-70% yield. [{1,4-(AgPPh2)2C6H4)}{Pt3(µ2-CO)3(PCy3)3}2][CF3SO3]2 (4). Anal. Calcd for C146H222Ag2F6O12P8Pt6S2: C, 44.04; H, 5.62. Found: C, 44.19; H, 6.24. IR: ν(CO) ) 1793 vs, 1765 m. [{1,4-(AgPPh2)2C6H4)}{Pt3(µ2-CO)(µ2-CNXyl)2(CNXyl)(PCy3)2}2][CF3SO3]2 (7). Anal. Calcd for C160H210Ag2F6N6S2O8P6Pt6: IR: ν(CN,term.) ) 2115 s; ν(CN,µ2), ν(CO) ) 1768 s, 1720 m. [{1,4-(AgPCy2CH2)2C6H4)}{Pt3(µ2-CO)(µ2-CNXyl)2(CNXyl)(PCy3)2}2] [CF3SO3]2 (20). Anal. Calcd for C162H238Ag2 F6N6S2O8P6Pt6 IR: ν(CN,term.) ) 2120 s; ν(CN,µ2), ν(CO) ) 1771 s, 1723 m. [{[1,1′-(AgPPh2)2Fe(η-C5H5)2}{Pt3(µ2-CO)3(PCy3)3}2] [CF3SO3]2 (25). Anal. Calcd for C150H226Ag2F6FeO12P8Pt6S2: C, 44.06; H 5.57. Found: C, 44.52; H, 6.52. IR: ν(CO) ) 1793 st, 1766 m. General Preparation of Double Gold Compounds. [ClAuPR2R′PR2AuCl] (0.016 mmol) and TlPF6 (0.033 mmol) were dissolved in thf (2 mL). The mixture was added dropwise to a solution of [Pt3(µCO)3(PCy3)3], [Pt3(µ-CNXyl)2(µ-CO)(CNXyl)(PCy3)2], or [Pt3(µCNXyl)3(CNXyl)2(PCy3)] (0.033 mmol) in CH2Cl2 (5 mL). After stirring for 10 min, the solution was concentrated. The resultant solid was dissolved in CH2Cl2, filtered through Celite, concentrated to 2 mL, and precipitated with hexane as deep-red crystals in 65-95% yield. [{1,4-(AuPPh2)2C6H4)}{Pt3(µ2-CO)3(PCy3)3}2][PF6]2 (5). Anal. Calcd for C144H222Au2F12O6P10Pt6: C, 41.66; H 5.39. Found: C, 42.89; H, 5.62. IR: ν(CO) ) 1798 vs, 1785 sh s. [{1,4-(AuPCy2)2C6H4)}{Pt3(µ2-CO)3(PCy3)3}2][PF6]2 (11). Anal. Calcd for C144H246Au2F12O6P10Pt6: C, 41.42; H 5.94. Found: C, 41.50; H, 5.91. IR: ν(CO) ) 1800 vs, 1770 m. MS (FAB+): 4030 (100, [MPF6]+), 3946 (4, [MPF6 - CyH]+), 3885 (26, [M]+), 3862 (20, [MPF6 - 2CyH]+), 2420 (10), 2093 (39), 1942 (49, [M]2+), 1897 (10), 1858 (15), 752 (13), 751 (32, [AuPCy3PCy2Ph]+), 749 (15). High resolution MS (FAB+, [MPF6]+): found, 4024.3 (13), 4025.3 (30), 4026.3 (50), 4027.3 (68), 4028.3 (87), 4029.3 (98), 4030.2 (100), 4031.3 (90), 4032.3 (75), 4033.3 (60), 4034.2 (40), 4035.2 (28), 4036.3 (18), 4037.1 (10), 4038.2 (7), 4039.3 (3); calcd, 4021 (0.26), 4022 (0.97), 4023 (3.18), 4024 (8.95), 4025 (20.66), 4026 (39.12), 4027 (61.70), 4028 (82.82),4029 (96.65), 4030 (100.00), 4031 (93.15), 4032 (79.05), 4033 (61.61), 4034 (44.41), 4035 (29.76), 4036 (18.62), 4037 (10.90), 4038 (5.99), 4039 (3.09), 4040 (1.50), 4041 (0.69), 4042 (0.30), 4043 (0.12). [{1,4-(AuPPh2CH2)2C6H4)}{Pt3(µ2-CO)3(PCy3)3}2][PF6]2 (14). Anal. Calcd for C146H226Au2F12O6P10Pt6: C, 41.96; H, 5.45. Found: C, 40.99; H, 5.34. IR: ν(CO) ) 1800 vs, 1772 w. MS (FAB+): 4034 (100, [MPF6]+), 3950 (6, [MPF6 - CyH]+), 3889 (25, [M]+), 3866 (45, [MPF6

1820 Inorganic Chemistry, Vol. 36, No. 9, 1997 - 2 CyH]+), 2424 (7), 2097 (43), 1995 (24), 1944 (28, [M]2+), 1860 (26), 1147 (11), 953 (16), 874 (14), 843 (10), 756 (10). High resolution MS (FAB+, [MPF6]+): found, 4028.4 (8),4029.4 (19), 4030.4 (46), 4031.4 (51), 4032.4 (75), 4033.4 (85), 4034.4 (100.00), 4035.4 (96), 4036.4 (86), 4037.5 (70), 4038.4 (60), 4039.4 (43), 4040.3 (26), 4041.3 (18); calcd, 4025 (0.26), 4026 (0.95), 4027 (3.14), 4028 (8.85),4029 (20.45), 4030 (38.79), 4031 (61.31), 4032 (82.47), 4033 (96.45), 4034 (100.00), 4035 (93.34), 4036 (79.37), 4037 (61.99), 4038 (44.77), 4039 (30.06), 4040 (18.84), 4041 (11.05), 4042 (6.09), 4043 (3.15), 4044(1.53), 4045 (0.7), 4046 (0.3), 4047(0.12). [{1,4-(AuPCy2CH2)2C6H4)}{Pt3(µ2-CO)3(PCy3)3}2][PF6]2 (17). Anal. Calcd for C146H250Au2F12O6P10Pt6: C, 41.72; H, 5.99. Found: C, 41.58; H, 5.69. IR: ν(CO) ) 1798 vs, 1768 m. [{1,3,5-(AuPPh2)3C6H3)}{Pt3(µ2-CO)3(PCy3)3}3][PF6]3 (21). Anal. Calcd for C213H330Au3F18O9P15Pt9: C, 41.34; H, 5.38. Found: C, 42.43; H, 5.26. IR: ν(CO) ) 1799 vs, 1778 sh m. [{1,4-(AuPPh2)2C6H4)}{Pt3(µ2-CO)(µ2-CNXyl)2(CNXyl)(PCy3)2}2][PF6]2 (8). Anal. Calcd for C158H210Au2F12N6O2P8Pt6: C, 44.49; H, 4.96; N, 1.97. Found: C, 44.90; H, 5.19; N, 1.81. IR: ν(CN,term.) ) 2134 s; n(CN,µ), ν(CO) ) 1850 w, 1779 s, 1732 m, 1584 w. [{1,4-(AuPCy2CH2)2C6H4)}{Pt3(µ2-CO)(µ2-CNXyl)2(CNXyl)(PCy3)2}2][PF6]2 (20). Anal. Calcd for C160H238Au2F12N6O2P8Pt6: C, 44.51; H, 5.56; N, 1.95. Found: C, 43.11; H, 5.55; N, 1.88. IR: ν(CN,term.) ) 2132 s; ν(CN,µ2), ν(CO) ) 1852 sh w, 1778 s, 1728 s, 1585 m. [{1,4-(AuPPh2)2C6H4)}{Pt3(µ2-CNXyl)3(CNXyl)2(PCy3)}2][PF6]2 (23). Anal. Calcd for C156H180Au2F12N10P6Pt6: C, 44.89; H, 4.32; N, 3.36. Found: C, 45.15; H, 4.96; N, 3.18. IR: ν(CN) ) 2132 vs; 1772 m, 1718 br s, 1584 m. [{1,4-(AuPCy2CH2)2C6H4)}{Pt3(µ2-CNXyl)3(CNXyl)2(PCy3)}2][PF6]2 (24). Anal. Calcd for C158H208Au2F12N10P6Pt6: C, 44.91; H, 4.96; N, 3.31. Found: C, 45.20; H, 5.20; N, 3.04. IR: ν(CN) ) 2124 vs, 1975 w, 1724 br s, 1584 m. [{[1,1′-(AuPPh2)2Fe(η-C5H5)2}{Pt3(µ2-CO)3(PCy3)3}2][PF6]2 (27). Anal. Calcd for C148H226Au2F12FeO6P10Pt6: C, 41.73; H, 5.35. Found: C, 41.34; H, 5.18. IR: ν(CO) ) 1799 st, 1769 m. MS (FAB+): 4112 (100, [MPF6]+), 4029 (8, [MPF6 - CyH]+), 3968 (10, [M]+), 3946 (66, [MPF6 - 2 CyH]+), 2420 (22), 2374 (48), 1992 (28), 1897 (78), 1226 (62), 954 (41), 875 (40), 751 (85). High resolution MS (FAB+, [MPF6]+): found, 4106.6 (6), 4107.6 (16), 4108.6 (30), 4109.6 (55),4110.8 (76), 4111 (95), 4112.6 (100), 4113.6 (96), 4114.6 (86), 4115.6 (77), 4116.6 (63), 4117.6 (48), 4118.6 (32), 4119.6 (19), 4120.6 (13), 4121.6 (8); calcd, 4106 (1.39), 4107 (4.09), 4108 (10.44), 4109 (22.56),4110 (41.00), 4111 (63.13), 4112 (83.61), 4113 (96.92), 4114 (100.00), 4115 (93.12), 4116 (79.13), 4117 (61.84), 4118 (44.73), 4119 (30.10), 4120 (18.92), 4121 (11.14), 4122 (6.16), 4123 (3.20), 4124(1.57), 4125 (0.72), 4126 (0.31), 4127(0.13). X-ray Crystal Structure Analysis. Collection, Reduction, and Refinement of X-ray Data. Crystals of 14 were crystallized as described above from a mixture of chloroform and cyclohexane. A crystal, which showed no defects and a perfect extinction under polarized light, was drawn up with solvent into a glass capillary and mounted on a STOE IPDS scanner with an image plate detector for the determination of the lattice parameters and for the data collection. The lattice parameters were obtained by a pattern fit of 524 reflections in the range 6.3-45.0° collected at 4 different φ angles, which differ 45° from each other successively and thus yield a good selection of reciprocal space. Because of the unit cell contents and the approximately spherical shape of the crystal, an absorption correction did not seem necessary. A total of 22 445 reflections were collected and 1459 were rejected because of boundary errors between different images. Intensities with F < 5 were cut off because the accuracy of the intensities was not sufficient according to several check measurements on a four-circle diffractometer (STOE STADI 4). Therefore 15 941 reflections were

Imhof et al. Table 6. Crystallographic Data for [{Pt3(µ-CO)3(PCy3)3}2{(AuPPh2)2(CH2)2C6H4)}][PF6]2‚2CHCl3‚2C6H12 chem formula ) C174H278O6F12P12Cl12P12Pt6Au2 fw ) 4993.54 a ) 15.350(3) Å b ) 17.150(3) Å c ) 20.446(4) Å R ) 84.54(3)° β ) 84.84(3)° γ ) 64.56(3)° V ) 4831(2) Å3

space group ) P1h Z)1 δ )1.716 g/cm3 µ ) 6.148 mm-1 T ) -123 °C λ ) 0.710 73 Å Rwa ) 0.0990 Rb ) 0.0435

a wR ) (∑w(Fo2Fc2)2/∑w(Fo2)2)1/2; w ) 1/(σ2(Fo2)+ (aP)2 + bP); P ) (Fo2(g0) + 2Fc2)/3. b R ) ∑||Fo| - |Fc||/∑|Fo| (n ) number of reflections; p ) number of parameters).

considered as observed, of which 8443 were independent and used for the structure determination and the final refinement of the structure. The structure was solved by direct and Fourier methods using the SHELXTL PLUS38 and SHELXL9339 packages. Refinement was carried out by full-matrix least squares of 1000 parameters. The parameters of the solvent atoms were refined by rigid bond and similar displacement parameter restraints. Weighted R-factors wR and all goodness of fits are based on F2 values. Conventional R-factors R are based on F values. (R-factors based on F2 are in general about twice as large as conventional ones based on F.) The weighting function was 1/[σ2(F2) + (0.021P)2 + 32.37P], with P ) [Fo2 + 2Fc2]/3. Experimental and crystallographic details are shown in Table 6 and in the Supporting Information. The cyclohexyl groups and the solvent molecules were to a certain extent disordered, which leads to large displacement parameters. An acentric model can be ruled out, because in this case the heavy atom parameters are strongly correlated and the data/parameter ratio becomes rather small. The positions of the hydrogen atoms were calculated by the default values of the SHELXL 93 program for 150 K, and the displacement parameters are 1.2 times as large as those of the corresponding nearest carbon atoms. These values were refined by riding the hydrogen parameters on the parameters of the carbon neighbors. The final atom coordinates and isotropic displacement parameters of the structure determination are given in the Supporting Information.

Acknowledgment. We are grateful for the financial support of the the Schweizerischen Schulrat (D.I., K.-H.D.) and the Bundesamt fu¨r Energiewirtschaft (F.J.). We gratefully acknowledge the use of the SHELXTL PLUS software of the Institut fu¨r Kristallographie of the ETH Zu¨rich. We thank Dr. Amrein for the FAB measurements. Supporting Information Available: NMR spectroscopy, including spectra of 3 and 4 (Figures S1 and S2), δ(P) of doubleand half-sandwich clusters as a function of different metals (Figure S3), 1J(Pt,P) in half-sandwich and double clusters as a function of different metals (Figure S4), 31P{1H}-NMR data for phosphines, biand trifunctional gold phosphine chlorides, and clusters (Tables S1S4) and ∆1J(Pt,P) values (Table S5), and crystallography tables, including crystal data and structure refinement for 14, atomic coordinates and equivalent isotropic displacement parameters, bond lengths and angles, anisotropic displacement parameters, and hydrogen coordinates and isotropic displacement parameters (Tables SS1-SS5) (26 pages). Ordering information is given on any current masthead page. 31P{1H}-NMR

IC960846X (38) SHELXLTL Plus Release 4.0, Siemens X-ray Instr. Inc., USA, 1990. (39) SHELXL93: Sheldrick, G. M. Universita¨t Go¨ttingen, Germany, 1993.